Planetary gear train of automatic transmission for vehicle

ABSTRACT

Nine forward speeds and one reverse speed are achieved by a planetary gear train of an automatic transmission that includes a main shifting portion having three planetary gear sets arranged on an input shaft, an auxiliary shifting portion having one planetary gear set arranged on an output shaft, ten shafts respectively connected with corresponding rotational elements of the four planetary gear sets, and two transfer gears respectively forming external gear-engagement between the main and auxiliary shifting portions.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2016-0170766, filed on Dec. 14, 2016, which isincorporated herein by reference in its entirety.

FIELD

The present disclosure relates to an automatic transmission for avehicle.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Recently, increase of oil price leads more competition for improvingfuel efficiency of a vehicle.

In this sense, research on an automatic transmission has been performedto simultaneously provide better drivability and fuel consumption byachieving more shift stages.

In order to achieve more shift stages for an automatic transmission, thenumber of parts is typically increased, which may deteriorateinstallability, production cost, weight and/or power flow efficiency.

Therefore, in order to enhance fuel efficiency of an automatictransmission through more shift stages with reduced number ofcomponents, a planetary gear train for an automatic transmissionenabling more shift-stages has been developed.

We have discovered that since an automatic transmission for eight ormore shift-stages typically includes three to four planetary gear setsand five to six engagement elements (frictional elements), and thetransmission may easily become lengthy, thereby deterioratinginstallability.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the present disclosureand therefore it may contain information that does not form the priorart that is already known to a person of ordinary skill in the art.

SUMMARY

The present disclosure provides a planetary gear train of an automatictransmission for a vehicle having advantages of realizing at least nineforward speeds and at least one reverse speed by a combination of fourplanetary gear sets, two external gears and six engagement elements,thereby providing improvement of power delivery performance and fuelconsumption and improving installability by reducing a length.

In addition, a wide available range of varying gear teeth of transfergears enables easily obtaining desired gear ratios for respectivevehicles, thereby improving power delivery performance and fuelconsumption.

In one form of the present disclosure, a planetary gear train includes:first, second, third, and fourth planetary gear sets, first and secondexternally-engaged gear sets, an input shaft, and an output shaft. Thefirst planetary gear set forms first, second, and third rotationalelements. The second planetary gear set forms fourth, fifth, and sixthrotational elements. The third planetary gear set forms seventh, eighth,and ninth rotational elements. The fourth planetary gear set formstenth, eleventh, and twelfth rotational elements. The firstexternally-engaged gear set forms thirteenth and fourteenth rotationalelements. The second externally-engaged gear set forms fifteenth andsixteenth rotational elements. The input shaft is disposed coaxial withthe first, second, and third planetary gear sets. The output shaft isdisposed in parallel with the input shaft and coaxial with the fourthplanetary gear set. The first rotational element and the seventhrotational element are connected with the tenth rotational elementthrough the second externally-engaged gear set. The second rotationalelement is fixedly connected with the input shaft. The twelfthrotational element is selectively connected with a transmission housing.The third rotational element is selectively externally-engaged with theeleventh rotational element that is fixedly connected with the outputshaft.

The exemplary gear train may further include first to tenth shafts. Thefirst shaft may be fixedly connected with the first rotational elementand the seventh rotational element. The second shaft may be fixedlyconnected with the second rotational element, the fifth rotationalelement, and the input shaft. The third shaft may be fixedly connectedwith the third rotational element and connected with the thirteenthrotational element. The fourth shaft may be fixedly connected with thefourth rotational element and fixedly connected with the transmissionhousing. The fifth shaft may be fixedly connected with the sixthrotational element. The sixth shaft may be fixedly connected with theeighth rotational element and selectively connected with the fifthshaft. The seventh shaft may be fixedly connected with the ninthrotational element, selectively connected with the fifth shaft, andselectively connected with the transmission housing. The eighth shaftmay be fixedly connected with the tenth rotational element andexternally gear-meshed with the first shaft. The ninth shaft may befixedly connected with the eleventh rotational element, selectivelyexternally-engaged with the third shaft, and fixedly connected with theoutput shaft. The tenth shaft may be fixedly connected with the twelfthrotational element and selectively connected with the transmissionhousing.

In an exemplary form, two shafts among the first shaft, the sixth shaft,and the seventh shaft may be selectively interconnected, such that thethird planetary gear set integrally rotate when the two shafts areconnectedly operated.

An exemplary gear train may further include: a first clutch arrangedbetween the second shaft and the seventh shaft, a second clutch arrangedbetween the first shaft and the sixth shaft, a third clutch arrangedbetween the ninth shaft and the fourteenth rotational element, a fourthclutch arranged between the fifth shaft and the sixth shaft, a firstbrake arranged between the seventh shaft and the transmission housing,and a second brake arranged between the tenth shaft and the transmissionhousing.

In one form, an gear train may further include: a first clutch arrangedbetween the second shaft and the seventh shaft, a second clutch arrangedbetween the first shaft and the seventh shaft, a third clutch arrangedbetween the ninth shaft and the fourteenth rotational element, a fourthclutch arranged between the fifth shaft and the sixth shaft, a firstbrake arranged between the seventh shaft and the transmission housing,and a second brake arranged between the tenth shaft and the transmissionhousing.

In another form, an exemplary gear train may further include: a firstclutch arranged between the second shaft and the seventh shaft, a secondclutch arranged between the sixth shaft and the seventh shaft, a thirdclutch arranged between the ninth shaft and the fourteenth rotationalelement, a fourth clutch arranged between the fifth shaft and the sixthshaft, a first brake arranged between the seventh shaft and thetransmission housing, and a second brake arranged between the tenthshaft and the transmission housing.

An exemplary gear train may further include: a first clutch arrangedbetween the second shaft and the seventh shaft, a second clutch arrangedbetween the first shaft and the sixth shaft, a third clutch arrangedbetween the third shaft and the thirteenth rotational element, a fourthclutch arranged between the fifth shaft and the sixth shaft, a firstbrake arranged between the seventh shaft and the transmission housing,and a second brake arranged between the tenth shaft and the transmissionhousing.

An exemplary gear train may further include: a first clutch arrangedbetween the second shaft and the seventh shaft, a second clutch arrangedbetween the first shaft and the seventh shaft, a third clutch arrangedbetween the third shaft and the thirteenth rotational element, a fourthclutch arranged between the fifth shaft and the sixth shaft, a firstbrake arranged between the seventh shaft and the transmission housing,and a second brake arranged between the tenth shaft and the transmissionhousing.

An exemplary gear train may further include: a first clutch arrangedbetween the second shaft and the seventh shaft, a second clutch arrangedbetween the sixth shaft and the seventh shaft, a third clutch arrangedbetween the third shaft and thirteenth rotational element, a fourthclutch arranged between the fifth shaft and the sixth shaft, a firstbrake arranged between the seventh shaft and the transmission housing,and a second brake arranged between the tenth shaft and the transmissionhousing.

The first planetary gear set may include: a first sun gear as the firstrotational element, a first planet carrier as the second rotationalelement, and a first ring gear as the third rotational element. Thesecond planetary gear set may include a second sun gear as the fourthrotational element, a second planet carrier as the fifth rotationalelement, and a second ring gear as the sixth rotational element. Thethird planetary gear set may include a third sun gear as the seventhrotational element, a third planet carrier as the eighth rotationalelement, and a third ring gear as the ninth rotational element. Thefourth planetary gear set may include a fourth sun gear as the tenthrotational element, a fourth planet carrier as the eleventh rotationalelement, and a fourth ring gear as the twelfth rotational element.

The first planetary gear set may be a single pinion planetary gear set.The second planetary gear set may be a double pinion planetary gear set.The third planetary gear set may be a double pinion planetary gear set.The fourth planetary gear set may be a single pinion planetary gear set.

According to a planetary gear train according to an exemplary form ofthe present disclosure, planetary gear sets are dividedly arranged oninput and output shafts disposed in parallel, thereby reducing a lengthand improving installability.

According to a planetary gear train according to an exemplary form ofthe present disclosure, at least eight forward speeds and at least onereverse speed may be realized by employing two externally engagedtransfer gears in addition to a combination of planetary gear sets,thereby providing a wide range of varying gear teeth so as to easilyachieve desired gear ratio and to easily comply with desired performancefor respective vehicles.

In addition, according to a planetary gear train according to anexemplary form of the present disclosure, a gear ratio span of more than9.7 may be achieved while realizing at least nine forward speeds and atleast one reverse speed, thereby increasing an engine drivingefficiency.

In addition, the linearity of step ratios of shift stages is securedwhile multi-staging the shift stage with high efficiency, thereby makingit possible to improve drivability such as acceleration before and aftera shift, an engine speed rhythmic sense, and the like.

Further, effects that can be obtained or expected from exemplary formsof the present disclosure are directly or suggestively described in thefollowing detailed description. That is, various effects expected fromexemplary forms of the present disclosure will be described in thefollowing detailed description.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a planetary gear train according to afirst exemplary form of the present disclosure;

FIG. 2 is an operational chart for respective engagement elements atrespective shift-stages in a planetary gear train according to a firstexemplary form of the present disclosure;

FIG. 3 is a schematic diagram of a planetary gear train according to asecond exemplary form of the present disclosure;

FIG. 4 is a schematic diagram of a planetary gear train according to athird exemplary form of the present disclosure;

FIG. 5 is a schematic diagram of a planetary gear train according to afourth exemplary form of the present disclosure;

FIG. 6 is a schematic diagram of a planetary gear train according to afifth exemplary form of the present disclosure;

FIG. 7 is a schematic diagram of a planetary gear train according to asixth exemplary form of the present disclosure;

FIG. 8 is a schematic diagram of a planetary gear train according to aseventh exemplary form of the present disclosure;

FIG. 9 is a schematic diagram of a planetary gear train according to aneighth exemplary form of the present disclosure;

FIG. 10 is a schematic diagram of a planetary gear train according to aninth exemplary form of the present disclosure;

FIG. 11 is a schematic diagram of a planetary gear train according to atenth exemplary form of the present disclosure;

FIG. 12 is a schematic diagram of a planetary gear train according to aeleventh exemplary form of the present disclosure; and

FIG. 13 is a schematic diagram of a planetary gear train according to atwelfth exemplary form of the present disclosure.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The present disclosure will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary forms of thepresent disclosure are shown. As those skilled in the art would realize,the described forms may be modified in various different ways, allwithout departing from the spirit or scope of the present disclosure.

The drawings and description are to be regarded as illustrative innature and not restrictive, and like reference numerals designate likeelements throughout the specification.

In the following description, dividing names of components into first,second and the like is to divide the names because the names of thecomponents are the same as each other and an order thereof is notparticularly limited.

FIG. 1 is a schematic diagram of a planetary gear train according to afirst exemplary form of the present disclosure.

Referring to FIG. 1, a planetary gear train includes: an input shaft IS,an output shaft OS, first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4, first and second transfer gears TF1 and TF2 asfirst and second externally-engaged gear sets, and engagement elementsof four clutches C1, C2, C3, and C4 and two brakes B1 and B2.

The input shaft IS is an input member and the torque from a crankshaftof an engine is input into the input shaft IS, after beingtorque-converted through a torque converter.

The output shaft OS is an output member, and, arranged in parallel withthe input shaft IS, outputs a shifted driving torque to a drive shaftthrough a differential apparatus.

The first, second, and third planetary gear sets PG1, PG2, and PG3 arearranged at external circumference of the input shaft IS and form a mainshifting portion. The first, second, and third planetary gear sets PG1,PG2, and PG3 are arranged in the order of the first, second, and thirdplanetary gear sets PG1, PG2, and PG3 from an engine side.

The fourth planetary gear set PG4 is arranged at external circumferenceof the output shaft OS disposed in parallel with the input shaft IS andforms an auxiliary shifting portion.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1 thatsupports first pinion P1 externally engaged with the first sun gear S1,and a first ring gear R1 that is internally engaged with the firstpinion P1. The first sun gear S1 acts as a first rotational element N1,the first planet carrier PC1 acts as a second rotational element N2, andthe first ring gear R1 acts as a third rotational element N3.

The second planetary gear set PG2 is a double pinion planetary gear set,and includes a second sun gear S2, a second planet carrier PC2 thatrotatably supports a second pinion P2 externally gear-meshed with thesecond sun gear S2, and a second ring gear R2 that is internally engagedwith the second pinion P2. The second sun gear S2 acts as a fourthrotational element N4, the second planet carrier PC2 acts as a fifthrotational element N5, and the second ring gear R2 acts as a sixthrotational element N6.

The third planetary gear set PG3 is a double pinion planetary gear set,and includes a third sun gear S3, a third planet carrier PC3 thatrotatably supports a third pinion P3 externally gear-meshed with thethird sun gear S3, and a third ring gear R3 that is internally engagedwith the third pinion P3. The third sun gear S3 acts as a seventhrotational element N7, the third planet carrier PC3 acts as an eighthrotational element N8, and the third ring gear R3 acts as a ninthrotational element N9.

The fourth planetary gear set PG4 is a single pinion planetary gear set,and includes a fourth sun gear S4, a fourth planet carrier PC4 thatsupports fourth pinion P4 externally engaged with the fourth sun gearS4, and a fourth ring gear R4 that is internally engaged with the fourthpinion P4. The fourth sun gear S4 acts as a tenth rotational elementN10, the fourth planet carrier PC4 acts as an eleventh rotationalelement N11, and the fourth ring gear R4 acts as a twelfth rotationalelement N12.

In the arrangement of the first, second, and third planetary gear setsPG1, PG2, and PG3, the first rotational element N1 is fixedly connectedwith the seventh rotational element N7, the second rotational element N2is fixedly connected with the fifth rotational element N5, and sevenshafts TM1 to TM7 are formed.

Three shafts TM8 to TM10 are connected to the fourth planetary gear setPG4.

The ten shafts TM1 to TM10 are hereinafter described in detail.

The first shaft TM1 is fixedly connected with the first rotationalelement N1 (first sun gear S1) and the seventh rotational element N7(third sun gear S3).

The second shaft TM2 is fixedly connected with the second rotationalelement N2 (first planet carrier PC1) and the fifth rotational elementN5 (second planet carrier PC2), and fixedly connected with the inputshaft IS, thereby always acting as an input element.

The third shaft TM3 is fixedly connected with the third rotationalelement N3 (first ring gear R1).

The fourth shaft TM4 is fixedly connected with the fourth rotationalelement N4 (second sun gear S2), and fixedly connected with thetransmission housing H, thereby always acting as a fixed element.

The fifth shaft TM5 is fixedly connected with the sixth rotationalelement N6 (second ring gear R2).

The sixth shaft TM6 is connected with the eighth rotational element N8(third planet carrier PC3), selectively connected with the fifth shaftTMS, and selectively connected with the first shaft TM1.

The seventh shaft TM7 is fixedly connected with the ninth rotationalelement N9 (third ring gear R3), selectively connected with the secondshaft TM2, and selectively connected with the transmission housing H,thereby selectively acting as a fixed element.

The eighth shaft TM8 is fixedly connected with the tenth rotationalelement N10 (fourth sun gear S4), and externally gear-meshed with thefirst shaft TM1.

The ninth shaft TM9 is fixedly connected with the eleventh rotationalelement N11 (fourth planet carrier PC4), fixedly connected with theoutput shaft OS thereby always acting as an output element, andselectively gear-meshed with the third shaft TM3 externally.

The tenth shaft TM10 is fixedly connected with the twelfth rotationalelement N12 (fourth ring gear R4), and selectively connected with thetransmission housing H, thereby selectively acting as a fixed element.

The first and second transfer gears TF1 and TF2 formed asexternally-engaged gear sets deliver a shifted torque of the mainshifting portion having the first, second, and third planetary gear setsPG1, PG2, and PG3 to the auxiliary shifting portion having the fourthplanetary gear set PG4.

The first transfer gear TF1 includes a first transfer drive gear TF1 aand a first transfer driven gear TF1 b that are externally gear-meshedwith each other. The first transfer drive gear TF1 a acts as athirteenth rotational element N13 fixedly connected with the third shaftTM3, and the first transfer driven gear TF1 b acts as a fourteenthrotational element N14 fixedly connected with the ninth shaft TM9.Thereby, the third shaft TM3 and the ninth shaft TM9 are externallygear-meshed with each other through the first transfer gear TF1.

The second transfer gear TF2 includes a second transfer drive gear TF2 aand a second transfer driven gear TF2 b that are externally gear-meshedwith each other. The second transfer drive gear TF2 a acts as afifteenth rotational element N15 fixedly connected with the first shaftTM1, and the second transfer driven gear TF2 b acts as a sixteenthrotational element N16 fixedly connected with the eighth shaft TM8.Thereby, the first shaft TM1 and the eighth shaft TM8 are externallygear-meshed with each other through the second transfer gear TF2.

As a result, respective shafts externally gear-meshed by the first orsecond transfer gear TF1 or TF2 rotate in opposite directions, and thegear ratios of the first and second transfer gears TF1 and TF2 may bepreset in consideration of desired speed ratio of the transmission.

Each of the eleven shafts TM1 to TM11 may be a rotational member thatfixedly interconnects the input and output shafts and rotationalelements of the planetary gear sets PG1, PG2, PG3, and PG4, or may be arotational member that selectively interconnects a rotational element tothe transmission housing H, or may be a fixed member fixed to thetransmission housing H.

In the disclosure, when two or more members are described to be “fixedlyconnected”, where the member may be any of a shaft, an input shaft, anoutput shaft, a rotational member, and a transmission housing, it meansthat the fixedly connected members always rotate at a same speed.

When two or more members are described to be “selectively connected” byan engagement element, it means that the selectively connected membersrotates separately when the engagement element is not engaged, androtates at a same speed when the engagement element is engaged.

The engagement elements include the four clutches C1, C2, C3, and C4 andthe two brakes B1 and B2, and are arranged as follows.

The first clutch C1 is arranged between the second shaft TM2 and theseventh shaft TM7, such that the second shaft TM2 and the seventh shaftTM7 may selectively become integral.

The second clutch C2 is arranged between the first shaft TM1 and thesixth shaft TM6, such that the first shaft TM1 and the sixth shaft TM6may selectively become integral.

The third clutch C3 is arranged between the ninth shaft TM9 and thefourteenth rotational element N14 of the first transfer gear TF1, suchthat the ninth shaft TM9 and the fourteenth rotational element N14 ofthe first transfer gear TF1 may selectively become integral.

The fourth clutch C4 is arranged between the fifth shaft TM5 and thesixth shaft TM6, such that the fifth shaft TM5 and the sixth shaft TM6may selectively become integral.

The first brake B1 is arranged between the seventh shaft TM7 and thetransmission housing H, such that the seventh shaft TM7 may selectivelyact as a fixed element.

The second brake B2 is arranged between the tenth shaft TM10 and thetransmission housing H, such that the tenth shaft TM10 may selectivelyact as a fixed element.

The second clutch C2 enables the third planetary gear set PG3 tointegrally rotate, and for such a purpose the second clutch C2 isdescribed to selectively connect the first shaft TM1 and the sixth shaftTM6, in the first exemplary form. It will be obviously understood thatthe same function and result may achieved by selectively connecting twoof the seventh, eighth, and ninth rotational elements N7, N8, and N9, oralternatively, by selectively connecting two shafts of the first shaftTM1, the sixth shaft TM6, and the seventh shaft TM7.

The engagement elements of the first, second, third, and fourth clutchesC1, C2, C3, and C4 and the first and second brakes B1 and B2 may berealized as multi-plate hydraulic pressure friction devices that arefrictionally engaged by hydraulic pressure, however, it should not beunderstood to be limited thereto, since various other configuration thatare electrically controllable may be available.

FIG. 2 is an operational chart for respective engagement elements atrespective shift-stages in a planetary gear train according to a firstexemplary form of the present disclosure.

Referring to FIG. 2, a planetary gear train according to a firstexemplary form of the present disclosure realizes shifting by operatingthree engagement elements among the four clutches C1, C2, C3, and C4 andthe two brakes B1 and B2.

[The Forward First Speed]

In the forward first speed D1, the second and fourth clutches C2 and C4and the second brake B2 are simultaneously operated.

As a result, third planetary gear set PG3 integrally rotates by theoperation of the second clutch C2, and the fifth shaft TM5 is connectedwith the sixth shaft TM6 by the operation of the fourth clutch C4. Inthis state, the torque of the input shaft IS is input to the secondshaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and the tenthshaft TM10 acts as a fixed element by the operation of the second brakeB2, thereby realizing the forward first speed by cooperative operationof respective shafts and outputting a shifted torque to the output shaftOS connected with the ninth shaft TM9.

[The Forward Second Speed]

In the forward second speed D2, the first and second clutch C1 and C2and the second brake B2 are simultaneously operated.

As a result, third planetary gear set PG3 integrally rotates by theoperation of the second clutch C2, and the second shaft TM2 is connectedwith the seventh shaft TM7 by the operation of the first clutch C1. Inthis state, the torque of the input shaft IS is input to the secondshaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and the tenthshaft TM10 acts as a fixed element by the operation of the second brakeB2, thereby realizing the forward second speed by cooperative operationof respective shafts and outputting a shifted torque to the output shaftOS connected with the ninth shaft TM9.

[The Forward Third Speed]

In the forward third speed D3, the first and fourth clutches C1 and C4and the second brake B2 are simultaneously operated.

As a result, the second shaft TM2 is connected with the seventh shaftTM7 by the operation of the first clutch C1, and the fifth shaft TM5 isconnected with the sixth shaft TM6 by the operation of the fourth clutchC4. In this state, the torque of the input shaft IS is input to thesecond shaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and the tenthshaft TM10 acts as a fixed element by the operation of the second brakeB2, thereby realizing the forward third speed by cooperative operationof respective shafts and outputting a shifted torque to the output shaftOS connected with the ninth shaft TM9.

[The Forward Fourth Speed]

In the forward fourth speed D4, the first and third clutches C1 and C3and the second brake B2 are simultaneously operated.

As a result, the second shaft TM2 is connected with the seventh shaftTM7 by the operation of the first clutch C1, and the ninth shaft TM9 isconnected with first transfer gear TF1 by the operation of the thirdclutch C3. In this state, the torque of the input shaft IS is input tothe second shaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and the tenthshaft TM10 acts as a fixed element by the operation of the second brakeB2, thereby realizing the forward fourth speed by cooperative operationof respective shafts and outputting a shifted torque to the output shaftOS connected with the ninth shaft TM9.

In addition, the forward fourth speed D4 may be realized bysimultaneously operating the third and fourth clutches C3 and C4 and thesecond brake B2.

In this case, the ninth shaft TM9 is connected with the first transfergear TF1 by the operation of the third clutch C3, and the fifth shaftTM5 is connected with the sixth shaft TM6 by the operation of the fourthclutch C4. In this state, the torque of the input shaft IS is input tothe second shaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and the tenthshaft TM10 acts as a fixed element by the operation of the second brakeB2, thereby realizing the forward fourth speed by cooperative operationof respective shafts and outputting a shifted torque to the output shaftOS connected with the ninth shaft TM9.

[The Forward Fifth Speed]

In the forward fifth speed D5, the first, third, and fourth clutches C1,C3, and C4 are simultaneously operated.

As a result, the second shaft TM2 is connected with the seventh shaftTM7 by the operation of the first clutch C1, the ninth shaft TM9 isconnected with the first transfer gear TF1 by the operation of the thirdclutch C3, and the fifth shaft TM5 is connected with the sixth shaft TM6by the operation of the fourth clutch C4. In this state, the torque ofthe input shaft IS is input to the second shaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, therebyrealizing the forward fifth speed by cooperative operation of respectiveshafts and outputting a shifted torque to the output shaft OS connectedwith the ninth shaft TM9.

[The Forward Sixth Speed]

In the forward sixth speed D6, the first, second, and third clutches C1,C2, and C3 are simultaneously operated.

As a result, third planetary gear set PG3 integrally rotates by theoperation of the second clutch C2, the second shaft TM2 is connectedwith the seventh shaft TM7 by the operation of the first clutch C1, andthe ninth shaft TM9 is connected with first transfer gear TF1 by theoperation of the third clutch C3. In this state, the torque of the inputshaft IS is input to the second shaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, therebyrealizing the forward sixth speed by cooperative operation of respectiveshafts and outputting a shifted torque to the output shaft OS connectedwith the ninth shaft TM9.

[The Forward Seventh Speed]

In the forward seventh speed D7, the second, third, and fourth clutchesC2, C3, and C4 are simultaneously operated.

As a result, third planetary gear set PG3 integrally rotates by theoperation of the second clutch C2, the ninth shaft TM9 is connected withthe first transfer gear TF1 by the operation of the third clutch C3, andthe fifth shaft TM5 is connected with the sixth shaft TM6 by theoperation of the fourth clutch C4. In this state, the torque of theinput shaft IS is input to the second shaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and thefourth shaft TM4 acts as a fixed element by the operation of the firstbrake B1, thereby realizing the forward seventh speed by cooperativeoperation of respective shafts and outputting a shifted torque to theoutput shaft OS connected with the ninth shaft TM9.

[The Forward Eighth Speed]

In the forward eighth speed D8, the second and third clutches C2 and C3and the first brake B1 are simultaneously operated.

As a result, third planetary gear set PG3 integrally rotates by theoperation of the second clutch C2, and the ninth shaft TM9 is connectedwith first transfer gear TF1 by the operation of the third clutch C3. Inthis state, the torque of the input shaft IS is input to the secondshaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and theseventh shaft TM7 acts as a fixed element by the operation of the firstbrake B1, thereby realizing the forward eighth speed by cooperativeoperation of respective shafts and outputting a shifted torque to theoutput shaft OS connected with the ninth shaft TM9.

[The Forward Ninth Speed]

In the forward ninth speed D9, the third and fourth clutches C3 and C4and the first brake B1 are simultaneously operated.

As a result, the ninth shaft TM9 is connected with the first transfergear TF1 by the operation of the third clutch C3, and the fifth shaftTM5 is connected with the sixth shaft TM6 by the operation of the fourthclutch C4. In this state, the torque of the input shaft IS is input tothe second shaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and theseventh shaft TM7 acts as a fixed element by the operation of the firstbrake B1, thereby realizing the forward ninth speed by cooperativeoperation of respective shafts and outputting a shifted torque to theoutput shaft OS connected with the ninth shaft TM9.

[The Reverse Speed]

In the reverse speed REV, the fourth clutch C4 and the first and secondbrakes B1 and B2 are simultaneously operated.

As a result, the fifth shaft TM5 is connected with the sixth shaft TM6by the operation of the fourth clutch C4. In this state, the torque ofthe input shaft IS is input to the second shaft TM2.

Then, the fourth shaft TM4 always acts as a fixed element, and theseventh shaft and the tenth shaft TM7 and TM10 acts as a fixed elementby the operation of the first and second brakes B1 and B2, therebyrealizing the reverse speed by cooperative operation of the shafts andoutputting a reverse torque through the output shaft OS connected withthe ninth shaft TM9.

FIG. 2 shows gear ratios calculated under the condition that the gearratio of the first ring gear R1/the first sun gear S1 is 2.40, the gearratio of the second ring gear R2/the second sun gear S2 is 2.61, thegear ratio of the third ring gear R3/the third sun gear S3 is 2.22, thegear ratio of the fourth ring gear R4/the fourth sun gear S4 is 2.13,the gear ratio of the first transfer driven gear TF1 b/the firsttransfer drive gear TF1 a is 1.01, and the gear ratio of the secondtransfer driven gear TF2 b/the second transfer drive gear TF2 a is 1.01.

FIG. 3 is a schematic diagram of a planetary gear train according to asecond exemplary form of the present disclosure.

In a planetary gear train according to a first exemplary form of thepresent disclosure shown in FIG. 1, the second clutch C2 enforcing thethird planetary gear set PG3 to integrally rotate is arranged betweenthe first shaft TM1 and the sixth shaft TM6. However, referring to FIG.3, the second clutch C2 is arranged between the first shaft TM1 and theseventh shaft TM7 in a planetary gear train according to a secondexemplary form.

As a result, the second exemplary form merely differs from a planetarygear train according to a first exemplary form in the location of thesecond clutch C2, and maintains operation and function of the firstexemplary form, which is therefore not described in further detail.

FIG. 4 is a schematic diagram of a planetary gear train according to athird exemplary form of the present disclosure.

In a planetary gear train according to a first exemplary form of thepresent disclosure shown in FIG. 1, the second clutch C2 enforcing thethird planetary gear set PG3 to integrally rotate is arranged betweenthe first shaft TM1 and the sixth shaft TM6. However, referring to FIG.4, the second clutch C2 is arranged between the sixth shaft TM6 and theseventh shaft TM7 in a planetary gear train according to a thirdexemplary form.

As a result, the third exemplary form merely differs from a planetarygear train according to a first exemplary form in the location of thesecond clutch C2, and maintains operation and function of the firstexemplary form, which is therefore not described in further detail.

FIG. 5 is a schematic diagram of a planetary gear train according to afourth exemplary form of the present disclosure.

In a planetary gear train according to a first exemplary form of thepresent disclosure shown in FIG. 1, the third clutch C3 is arrangedbetween the ninth shaft TM9 and the first transfer gear TF1. However,referring to FIG. 5, the third clutch C3 is arranged between the thirdshaft TM3 and the first transfer gear TF1 in a planetary gear trainaccording to a fourth exemplary form.

As a result, the fourth exemplary form merely differs from a planetarygear train according to a first exemplary form in the location of thethird clutch C3, and maintains operation and function of the firstexemplary form, which is therefore not described in further detail.

FIG. 6 is a schematic diagram of a planetary gear train according to afifth exemplary form of the present disclosure.

In a planetary gear train according to a second exemplary form of thepresent disclosure shown in FIG. 3, the third clutch C3 is arrangedbetween the ninth shaft TM9 and the first transfer gear TF1. However,referring to FIG. 6, the third clutch C3 is arranged between the thirdshaft TM3 and the first transfer gear TF1 in a planetary gear trainaccording to a fifth exemplary form.

As a result, the fifth exemplary form merely differs from a planetarygear train according to a second exemplary form in the location of thethird clutch C3, and maintains operation and function of the secondexemplary form, which is therefore not described in further detail.

FIG. 7 is a schematic diagram of a planetary gear train according to asixth exemplary form of the present disclosure.

In a planetary gear train according to a third exemplary form of thepresent disclosure shown in FIG. 4, the third clutch C3 is arrangedbetween the ninth shaft TM9 and the first transfer gear TF1. However,referring to FIG. 7, the third clutch C3 is arranged between the thirdshaft TM3 and the first transfer gear TF1 in a planetary gear trainaccording to a sixth exemplary form.

As a result, the sixth exemplary form merely differs from a planetarygear train according to a third exemplary form in the location of thethird clutch C3, and maintains operation and function of the thirdexemplary form, which is therefore not described in further detail.

FIG. 8 is a schematic diagram of a planetary gear train according to aseventh exemplary form of the present disclosure.

In a planetary gear train according to a first exemplary form of thepresent disclosure shown in FIG. 1, the first, second, and thirdplanetary gear sets PG1, PG2, and PG3 are arranged in the order of thefirst, second, and third planetary gear sets PG1, PG2, and PG3 from anengine side. However, in a planetary gear train according to a seventhexemplary form as illustrated in FIG. 8, the first, second, and thirdplanetary gear sets PG1, PG2, and PG3 are arranged in the order of thefirst, third, second planetary gear sets PG1, PG3, and PG2 from theengine side.

As a result, the seventh exemplary form merely differs from a planetarygear train according to a first exemplary form in the location of thefirst, second, and third planetary gear sets PG1, PG2, and PG3, andmaintains operation and function of the first exemplary form, which istherefore not described in further detail.

FIG. 9 is a schematic diagram of a planetary gear train according to aneighth exemplary form of the present disclosure.

In a planetary gear train according to a seventh exemplary form of thepresent disclosure shown in FIG. 8, the second clutch C2 enforcing thirdplanetary gear set PG3 to integrally rotate is arranged between thefirst shaft TM1 and the sixth shaft TM6. However, referring to FIG. 9,the second clutch C2 is arranged between the first shaft TM1 and theseventh shaft TM7 in a planetary gear train according to an eighthexemplary form.

As a result, the eighth exemplary form merely differs from a planetarygear train according to a seventh exemplary form in the location of thesecond clutch C2, and maintains operation and function of the seventhexemplary form, which is therefore not described in further detail.

FIG. 10 is a schematic diagram of a planetary gear train according to aninth exemplary form of the present disclosure.

In a planetary gear train according to a seventh exemplary form of thepresent disclosure shown in FIG. 8, the second clutch C2 enforcing thirdplanetary gear set PG3 to integrally rotate is arranged between thefirst shaft TM1 and the sixth shaft TM6. However, referring to FIG. 10,the second clutch C2 is arranged between the sixth shaft TM6 and theseventh shaft TM7 in a planetary gear train according to the ninthexemplary form.

As a result, the ninth exemplary form merely differs from a planetarygear train according to a seventh exemplary form in the location of thesecond clutch C2, and maintains operation and function of the seventhexemplary form, which is therefore not described in further detail.

FIG. 11 is a schematic diagram of a planetary gear train according to atenth exemplary form of the present disclosure.

In a planetary gear train according to a seventh exemplary form of thepresent disclosure shown in FIG. 8, the third clutch C3 is arrangedbetween the ninth shaft TM9 and the first transfer gear TF1. However,referring to FIG. 11, the third clutch C3 is arranged between the firsttransfer gear TF1 and the third shaft TM3 in a planetary gear trainaccording to the tenth exemplary form.

As a result, the tenth exemplary form merely differs from a planetarygear train according to a seventh exemplary form in the location of thethird clutch C3, and maintains operation and function of the seventhexemplary form, which is therefore not described in further detail.

FIG. 12 is a schematic diagram of a planetary gear train according to aneleventh exemplary form of the present disclosure.

In a planetary gear train according to an eighth exemplary form of thepresent disclosure shown in FIG. 9, the third clutch C3 is arrangedbetween the ninth shaft TM9 and the first transfer gear TF1. However,referring to FIG. 12, the third clutch C3 is arranged between the firsttransfer gear TF1 and the third shaft TM3 in a planetary gear trainaccording to an eleventh exemplary form.

As a result, the eleventh exemplary form merely differs from a planetarygear train according to an eighth exemplary form in the location of thethird clutch C3, and maintains operation and function of the eighthexemplary form, which is therefore not described in further detail.

FIG. 13 is a schematic diagram of a planetary gear train according to atwelfth exemplary form of the present disclosure.

In a planetary gear train according to a ninth exemplary form of thepresent disclosure shown in FIG. 10, the third clutch C3 is arrangedbetween the ninth shaft TM9 and the first transfer gear TF1. However,referring to FIG. 13, the third clutch C3 is arranged between the firsttransfer gear TF1 and the third shaft TM3 in a planetary gear trainaccording to the twelfth exemplary form.

As a result, the twelfth exemplary form merely differs from a planetarygear train according to a ninth exemplary form in the location of thethird clutch C3, and maintains operation and function of the ninthexemplary form, which is therefore not described in further detail.

As described above, according to a planetary gear train according to anexemplary form of the present disclosure, at least nine forward speedsand at least one reverse speed may be realized by a combination of fourplanetary gear sets, two transfer gears, and five or six engagementelements, thereby providing improvement of power delivery performanceand fuel consumption and improving installability by shortening thelength of an automatic transmission.

In addition, according to a planetary gear train according to anexemplary form of the present disclosure, two transfer gears of externalgears arranged on the output shaft OS are employed in addition to threeplanetary gear sets, and thus, gear teeth may be widely varied so as toeasily achieve desired gear ratio and to easily comply with desiredperformance for respective vehicles.

In addition, according to a planetary gear train according to anexemplary form of the present disclosure, a gear ratio span of more than8.7 may be achieved while realizing at least nine forward speeds and atleast one reverse speed, thereby increasing an engine drivingefficiency.

In addition, the linearity of step ratios of shift stages is securedwhile multi-staging the shift stage with high efficiency, thereby makingit possible to improve drivability such as acceleration before and aftera shift, an engine speed rhythmic sense, and the like.

While this present disclosure has been described in connection with whatis presently considered to be practical exemplary forms, it is to beunderstood that the present disclosure is not limited to the disclosedforms, but, on the contrary, is intended to cover various modificationsand equivalent arrangements included within the spirit and scope of thepresent disclosure.

DESCRIPTION OF SYMBOLS

PG1, PG2, PG3, PG4: first, second, third, and fourth planetary gear sets

S1, S2, S3, S4: first, second, third, and fourth sun gears

PC1, PC2, PC3, PC4: first, second, third, and fourth planet carriers

R1, R2, R3, R4: first, second, third, and fourth ring gears

IS: input shaft

OS: output shaft

B1, B2: first and second brakes

C1, C2, C3, C4: first, second, third, and fourth clutches

TF1, TF2: first and second transfer gears

TM1, TM2, TM3, TM4, TMS, TM6, TM7, TM8, TM9, TM10: first, second, third,fourth, fifth, sixth, seventh, eighth, ninth, and tenth shafts

What is claimed is:
 1. A planetary gear train of claim of an automatictransmission for a vehicle, the planetary gear train comprising: a firstplanetary gear set having first, second, and third rotational elements;a second planetary gear set having fourth, fifth, and sixth rotationalelements; a third planetary gear set having seventh, eighth, and ninthrotational elements; a fourth planetary gear set having tenth, eleventh,and twelfth rotational elements; a first externally-engaged gear sethaving thirteenth and fourteenth rotational elements; a secondexternally-engaged gear set having fifteenth and sixteenth rotationalelements; an input shaft disposed coaxial with the first, second, andthird planetary gear sets; and an output shaft disposed in parallel withthe input shaft and coaxial with the fourth planetary gear set; whereinthe first rotational element and the seventh rotational element areconnected with the tenth rotational element through the secondexternally-engaged gear set, the second rotational element is fixedlyconnected with the input shaft, the twelfth rotational element isselectively connected with a transmission housing, and the thirdrotational element is selectively externally-engaged with the eleventhrotational element that is fixedly connected with the output shaft. 2.The planetary gear train of claim 1, further comprising: a first shaftfixedly connected with the first rotational element and the seventhrotational element; a second shaft fixedly connected with the secondrotational element, the fifth rotational element, and the input shaft; athird shaft fixedly connected with the third rotational element and thethirteenth rotational element; a fourth shaft fixedly connected with thefourth rotational element and fixedly connected with the transmissionhousing; a fifth shaft fixedly connected with the sixth rotationalelement; a sixth shaft fixedly connected with the eighth rotationalelement and selectively connected with the fifth shaft; a seventh shaftfixedly connected with the ninth rotational element, and selectivelyconnected with the fifth shaft and the transmission housing; an eighthshaft fixedly connected with the tenth rotational element and externallygear-meshed with the first shaft; a ninth shaft fixedly connected withthe eleventh rotational element, selectively externally-engaged with thethird shaft, and fixedly connected with the output shaft; and a tenthshaft fixedly connected with the twelfth rotational element andselectively connected with the transmission housing.
 3. The planetarygear train of claim 2, wherein two shafts selected from the first shaft,the sixth shaft, and the seventh shaft are selectively interconnected,such that the third planetary gear set integrally rotates when theselected two shafts are connectedly operated.
 4. The planetary geartrain of claim 3, further comprising: a first clutch arranged betweenthe second shaft and the seventh shaft; a second clutch arranged betweenthe first shaft and the sixth shaft; a third clutch arranged between theninth shaft and the fourteenth rotational element; a fourth clutcharranged between the fifth shaft and the sixth shaft; a first brakearranged between the seventh shaft and the transmission housing; and asecond brake arranged between the tenth shaft and the transmissionhousing.
 5. The planetary gear train of claim 3, further comprising: afirst clutch arranged between the second shaft and the seventh shaft; asecond clutch arranged between the first shaft and the seventh shaft; athird clutch arranged between the ninth shaft and the fourteenthrotational element; a fourth clutch arranged between the fifth shaft andthe sixth shaft; a first brake arranged between the seventh shaft andthe transmission housing; and a second brake arranged between the tenthshaft and the transmission housing.
 6. The planetary gear train of claim3, further comprising: a first clutch arranged between the second shaftand the seventh shaft; a second clutch arranged between the sixth shaftand the seventh shaft; a third clutch arranged between the ninth shaftand the fourteenth rotational element; a fourth clutch arranged betweenthe fifth shaft and the sixth shaft; a first brake arranged between theseventh shaft and the transmission housing; and a second brake arrangedbetween the tenth shaft and the transmission housing.
 7. The planetarygear train of claim 3, further comprising: a first clutch arrangedbetween the second shaft and the seventh shaft; a second clutch arrangedbetween the first shaft and the sixth shaft; a third clutch arrangedbetween the third shaft and the thirteenth rotational element; a fourthclutch arranged between the fifth shaft and the sixth shaft; a firstbrake arranged between the seventh shaft and the transmission housing;and a second brake arranged between the tenth shaft and the transmissionhousing.
 8. The planetary gear train of claim 3, further comprising: afirst clutch arranged between the second shaft and the seventh shaft; asecond clutch arranged between the first shaft and the seventh shaft; athird clutch arranged between the third shaft and the thirteenthrotational element; a fourth clutch arranged between the fifth shaft andthe sixth shaft; a first brake arranged between the seventh shaft andthe transmission housing; and a second brake arranged between the tenthshaft and the transmission housing.
 9. The planetary gear train of claim3, further comprising: a first clutch arranged between the second shaftand the seventh shaft; a second clutch arranged between the sixth shaftand the seventh shaft; a third clutch arranged between the third shaftand thirteenth rotational element; a fourth clutch arranged between thefifth shaft and the sixth shaft; a first brake arranged between theseventh shaft and the transmission housing; and a second brake arrangedbetween the tenth shaft and the transmission housing.
 10. The planetarygear train of claim 1, wherein: the first planetary gear set is a singlepinion planetary gear set and includes a first sun gear as the firstrotational element, a first planet carrier as the second rotationalelement, and a first ring gear as the third rotational element; thesecond planetary gear set is a double pinion planetary gear set andincludes a second sun gear as the fourth rotational element, a secondplanet carrier as the fifth rotational element, and a second ring gearas the sixth rotational element; the third planetary gear set is adouble pinion planetary gear set and includes a third sun gear as theseventh rotational element, a third planet carrier as the eighthrotational element, and a third ring gear as the ninth rotationalelement; and the fourth planetary gear set is a single pinion planetarygear set and includes a fourth sun gear as the tenth rotational element,a fourth planet carrier as the eleventh rotational element, and a fourthring gear as the twelfth rotational element.
 11. A planetary gear trainof claim of an automatic transmission for a vehicle, the planetary geartrain comprising: a first planetary gear set having first, second, andthird rotational elements; a second planetary gear set having fourth,fifth, and sixth rotational elements; a third planetary gear set havingseventh, eighth, and ninth rotational elements; a fourth planetary gearset having tenth, eleventh, and twelfth rotational elements; an inputshaft mounted with the first, second, and third planetary gear sets onan external circumference of the input shaft; and an output shaftdisposed in parallel with the input shaft and mounted with the fourthplanetary gear set on an external circumference of the output shaft,wherein the first rotational element is fixedly connected with theseventh rotational element, the second rotational element is fixedlyconnected with the sixth rotational element and fixedly connected withthe input shaft, the fourth rotational element is fixedly connected witha transmission housing, the eighth rotational element is selectivelyconnected with the sixth rotational element, the ninth rotationalelement is selectively connected with the fifth rotational element andthe transmission housing, the tenth rotational element is externallygear-meshed with the seventh rotational element, the eleventh rotationalelement is fixedly connected with the output shaft and selectivelyexternally-engaged with the third rotational element, the twelfthrotational element is selectively connected with the transmissionhousing, and two transfer gears are respectively arranged between thethird and eleventh rotational elements and between the seventh and tenthrotational elements.
 12. The planetary gear train of claim 11, whereintwo rotational elements selected from the seventh, eighth, and ninthrotational elements are selectively interconnected, such that the thirdplanetary gear set integrally rotates when the selected two rotationalelements are engaged.
 13. The planetary gear train of claim 12, whereinthe two transfer gears comprises: a first transfer gear including: athirteenth rotational element fixedly connected with the thirdrotational element, and a fourteenth rotational element selectivelyconnected with the eleventh rotational element; and a second transfergear including: a fifteenth rotational element fixedly connected withthe seventh rotational element, and a sixteenth rotational elementfixedly connected with the tenth rotational element.
 14. The planetarygear train of claim 12, wherein the two transfer gears comprises: afirst transfer gear including: a thirteenth rotational elementselectively connected with the third rotational element, and afourteenth rotational element fixedly connected with the eleventhrotational element; and a second transfer gear including: a fifteenthrotational element fixedly connected with the seventh rotationalelement, and a sixteenth rotational element fixedly connected with thetenth rotational element.
 15. The planetary gear train of claim 13,further comprising: a first clutch selectively connecting the fifthrotational element and the ninth rotational element; a second clutchselectively connecting the seventh rotational element and the eighthrotational element; a third clutch selectively connecting the eleventhrotational element and the fourteenth rotational element; a fourthclutch selectively connecting the sixth rotational element and theeighth rotational element; a first brake arranged between the ninthrotational element and the transmission housing; and a second brakearranged between the twelfth rotational element and the transmissionhousing.
 16. The planetary gear train of claim 13, further comprising: afirst clutch selectively connecting the fifth rotational element and theninth rotational element; a second clutch selectively connecting theseventh rotational element and the ninth rotational element; a thirdclutch selectively connecting the eleventh rotational element and thefourteenth rotational element; a fourth clutch selectively connectingthe sixth rotational element and the eighth rotational element; a firstbrake arranged between the ninth rotational element and the transmissionhousing; and a second brake arranged between the twelfth rotationalelement and the transmission housing.
 17. The planetary gear train ofclaim 13, further comprising: a first clutch selectively connecting thefifth rotational element and the ninth rotational element; a secondclutch selectively connecting the eighth rotational element and theninth rotational element; a third clutch selectively connecting theeleventh rotational element and the fourteenth rotational element; afourth clutch selectively connecting the sixth rotational element andthe eighth rotational element; a first brake arranged between the ninthrotational element and the transmission housing; and a second brakearranged between the twelfth rotational element and the transmissionhousing.
 18. The planetary gear train of claim 14, further comprising: afirst clutch selectively connecting the fifth rotational element and theninth rotational element; a second clutch selectively connecting theseventh rotational element and the eighth rotational element; a thirdclutch selectively connecting the third rotational element and thethirteenth rotational element; a fourth clutch selectively connectingthe sixth rotational element and the eighth rotational element; a firstbrake arranged between the ninth rotational element and the transmissionhousing; and a second brake arranged between the twelfth rotationalelement and the transmission housing.
 19. The planetary gear train ofclaim 14, further comprising: a first clutch selectively connecting thefifth rotational element and the ninth rotational element; a secondclutch selectively connecting the seventh rotational element and theninth rotational element; a third clutch selectively connecting thethird rotational element and the thirteenth rotational element; a fourthclutch selectively connecting the sixth rotational element and theeighth rotational element; a first brake arranged between the ninthrotational element and the transmission housing; and a second brakearranged between the twelfth rotational element and the transmissionhousing.
 20. The planetary gear train of claim 14, further comprising: afirst clutch selectively connecting the fifth rotational element and theninth rotational element; a second clutch selectively connecting theeighth rotational element and the ninth rotational element; a thirdclutch selectively connecting the third rotational element and thethirteenth rotational element; a fourth clutch selectively connectingthe sixth rotational element and the eighth rotational element; a firstbrake arranged between the ninth rotational element and the transmissionhousing; and a second brake arranged between the twelfth rotationalelement and the transmission housing.